Detection of the optical bands of molybdenum(V) in DMSO reductase (Rhodobacter capsulatus) by low‐temperature MCD spectroscopy

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Abstract
Dimethylsulphoxide (DMSO) reductase from R. capsulatus contains a molybdenum‐pterin cofactor at its active site. As prepared the molybdenum is in the 6+ oxidation state, devoid of EPR signals. Stepwise reduction generates an EPR signal characteristic of Mo(V) having hyperfine coupling to a single proton and integrating to less than 25% of the total molybdenum. The low temperature MCD spectrum shows oppositely signed bands between ∼550–700 nm. These bands are assigned as dithiolene‐to‐Mo(V) charge transitions. A simple theoretical model can satisfactorily account for the bands in the MCD spectrum. No evidence is found for cysteine coordination to Mo(V).

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